First principles studies of oxygen adsorption on the γ-U (1 1 0) surface and influences of Mo doping

Abstract

By ab initio molecular dynamics (AIMD) simulations and density-functional theory (DFT) calculations, we studied the kinetics and energetics of oxygen absorption on clean and Mo-doped γ-U (1 1 0) surface. The AIMD simulations shows that O2 will dissociates into separate O atoms, which are finally adsorbed on the surface. The doping Mo can change the final adsorption sites of O atoms. In addition, we found that temperature can accelerate O2 dissociation on γ-U (1 1 0) surface.The calculation of adsorption energies shows that the most preferred site for O atoms on the γ-U (1 1 0) surface is the short bridge site, followed by the 3-fold hollow. The doping Mo will decrease the adsorption energies of all the adsorption sites. With Mo-doping, the most preferred site for O atom is still short bridge. But, the second preferred adsorption site become long bridge. For clean and Mo-doped surfaces, the on-top is the least preferred adsorption site for atomic oxygen. Through calculations of diffusion pathways, we found Mo-doping raise the energy barrier for O atom diffusion on the surface. By the calculated segregation energies, it is found that the Mo atom prefers to locate in γ-U “bulk” rather than the top layer of the surface.